Presence functionality in the h.323 protocol

ABSTRACT

A method providing presence functionality related to the H.323 protocol is disclosed. A Present Application Server (PAS) is holding a presence list for each user is introduced. The presence list of a first user comprises other network registered users for which the first user, according to a predefined request list stored in the PAS, wants to track the registration status. The present invention is applied to the H.323 standard, and the registration status of each user corresponds to the user&#39;s registration status in their associated Gatekeepers. Each time a change in registration status for a user occur in its associated Gatekeeper, the Gatekeeper will send a message including an identification of both the user and the Gatekeeper, in addition to information concerning the change of status (register or unregister). As a response to this, the presence lists affected by the change of the registration status of said user is updated in the PAS. Then the associated users are informed by messages sent from the PAS via the Gatekeeper to the user&#39;s EndPoints. The messages are adapted to refresh URL&#39;s at the EndPoints pointing at the user&#39;s presence list.

FIELD OF THE INVENTION

[0001] The present invention is related to packet-based multimediacommunication systems, especially presence functionality related to theH.323 protocol.

BACKGROUND OF THE INVENTION

[0002] Presence and chat applications (e.g. ICQ on the Internet) aregaining popularity. These applications are based on that the usersregister their presence and may be visible on other users contact orbuddy lists. An example of such an application is ICQ. ICQ is a presenceand chat service on the Internet. ICQ allows you to know which of yourfriends that are online, and you may use a variety of communicationtechniques to contact them. It is also integrated with MicrosoftNetMeeting.

[0003] This is for the time being the most common application, but otherpresence applications are expected to be common in the near future. Anexample of such an application is a localization application by which agroup of users are informed e.g. via a map on a terminal screen wherethe other users currently are positioned. The positions may be providedby a GPS receiver placed in each user's terminal. Especially this lastmentioned application or similar applications are expected to becomepopular services, and therefore, presence application will probablyoccur in an increasing number of associations.

[0004] As also IP telephony becomes more customary, it is clear thatthere is a need for solutions implementing presence applicationstherein. H.323 is today one of the most widespread protocol for IPtelephony or more generally for multimedia communication where theunderlying transport is a Packet Based Network. The description in thisapplication is applied to this protocol, and associated terminology,well known to persons skilled in the art, will be used.

[0005] According to the H.323 standard, user registration into a networkis arranged by so-called Gatekeepers.

[0006] The H.323 protocol describes/provides the procedure for the userregistration. The user registration is basically a relation between theuser identifiers (called aliases in H.323) e.g. E.164 numbers or e-mailaddresses and the users current IP address. See FIG. 1.

[0007] When a User A registers into the H.323 based system, itsendpoint, representing the users terminal, sends the information aboutthe IP address associated with that endpoint. This information isencapsulated in a registration request message (RRQ) and sent to a H323Gatekeeper (GK) (1). The relevant information from the RRQ message isthen stored in a dB (2). As an acknowledgement to the user about itsregistration, the GK responds with a registration confirmation message(RCF), (3). This is a normal registering procedure in H.323 basedsystems.

[0008] The User A is now recognised within the system under aliasesE164: 523 946, e-mail: userA@ipt.com and can be contacted onIP:111.12.11.17.

[0009] H.323 is based on users registering into a network, but there iscurrently no way to provide the already existing registration status(presence) to other users in the H.323. Consequently, there is currentlyno way other users can find out if User A is registered or not, and UserA can not notify his friends about his/hers presence in the system usingH.323.

[0010] ICQ is a presence and chat service on the Internet. ICQ allowsyou to know which of your friends that are online, and you may use avariety of communication techniques to contact them. It is alsointegrated with Microsoft NetMeeting, which in fact is a H.323 endpoint.

[0011] However, if you want to be registered into a H.323 network, youwould have to register both in ICQ and the H.323 network, and you willnot know if other users registered in ICQ also are registered in a H.323network. ICQ does not make use of the information already stored in theGatekeepers whether a user is logged in or not.

[0012] SIP is another protocol that may be used for IP telephony. SIP,like H.323, uses registrations to map user identifiers to host names andthereby IP addresses. SIP has proposed extensions for presence handling.The mechanism is based on that a user may send a SUBSCRIBE message tosubscribe to other users registrations, and will get a NOTIFY messagewhen one of these users changes his/her registration status.

[0013] However, this is a mechanism for SIP protocol, and is notapplicable for equipment using the H.323 protocol. Therefore, none ofthe above mentioned known solutions solve the problem of relatingpresence information to registration status in an H.323 network.

SUMMARY OF THE INVENTION

[0014] It is an object of the present invention to provide a method thateliminates the drawbacks described above. The features defined in theclaims enclosed characterize this method.

[0015] More specifically, the present invention introduces a PresentApplication Server (PAS) holding a presence list for each user. Thepresence list of a first user comprises other network registered usersfor which the first user, according to a predefined request list storedin the PAS, wants to track the registration status. However, accordingto a preferred embodiment of the present invention, a second user, nothaving the first user in an associated trust list, will not be includedin the presence list of the first user even if the second user both isregistered in the communication network and included in the request listof the first user.

[0016] The present invention is applied to the H.323 standard, and theregistration status of each user corresponds to the user's registrationstatus in their associated Gatekeepers. Each time a change inregistration status for a user occur in its associated Gatekeeper, theGatekeeper will send a message including an identification of both theuser and the Gatekeeper, in addition to information concerning thechange of status (register or unregister). As a response to this, thepresence lists affected by the change of the registration status of saiduser is updated in the PAS. Then the associated users are informed bymessages sent from the PAS via the Gatekeeper to the user's EndPoints.The messages are adapted to refresh URL's at the EndPoints pointing atthe user's presence list.

[0017] The present invention make use of the registration statusinformation already stored in the Gatekeepers. Then the users may bevisible for other users in a presence application just as they areattached to a Gatekeeper.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the invention more readily understandable, thediscussion that follows will refer to the accompanying drawings.

[0019]FIG. 1 shows a normal registration procedure in an H.323 basedsystem.

[0020]FIG. 2 is an overview of the system concept according to thepresent invention FIG. 3 shows the relationship between an H.323 GateKeeper and the Presence Application Server (PAS) according to thepresent invention.

[0021]FIG. 4 shows a registration procedure in an H.323 based systemusing Annex K according to the present invention.

DETAILED DESCRIPTION

[0022] The present invention introduces a Presence Application Server(PAS) communicating with one or more Gatekeepers. The PAS (PresenceApplication Server) is handling presence services. It is separated fromthe gatekeeper to make the system scalable. This is shown in FIG. 2. Bydoing this, the PAS may be shared by many gatekeepers, even gatekeepersbelonging to different H.323 operators.

[0023] According to the present invention, a User 1 will have both arequest list and a trusted list in the PAS. The request list containsall the users for which User 1 wants registration status. The trustedlist contains all the users that User 1 allows to be notified whenhis/her registration status changes.

[0024] The PAS has to correlate these lists with registration status andthereby make one presence list for User 1 containing the currentlyregistered users included in the request list of User 1. A user in thepresence list of User 1 also have to have User 1 included in its trustedlist. If not, the user will be excluded from the presence list of User 1even if it is both registered and included in the request list of User1.

[0025] This may be exemplified by the following tables including therequest lists and trust lists of User 1, User 2, User 3 and User 4,respectively. User Registered Request List Trust List User 1 GK A User2, User 3, User 4 User 2, User 3 User 2 No User 1, User 3 User 1, User 3User 3 GK B User 1, User 2, User 4 User 1, User 2, User 4 User 4 GK BUser 1, User 3 User 3

[0026] The PAS will in this case have the following compiled presencelists for the users: User Presence List User 1 User 3 User 2 Notregistered User 3 User 1, User 4 User 4 User 3

[0027] The connection between the GK and the PAS is structured with thePAS as a server and the GK as a client. Initially the GK may bepre-registered at the PAS. The protocol used between the GK and the PAS,may be a “presence protocol” (PP), which is known for persons skilled inthe art, and has the following characteristics:

[0028] The GK may be pre-registered at the PAS.

[0029] Provides a communication between the GK and PAS.

[0030] The GK sends messages related to user registrations to the PAS.

[0031] The PAS sends events related to user presence information to theGK's.

[0032] The messages sent to the PAS includes one or more user IDs, theID of the corresponding GK and the operation: register or unregister.The events sent from PAS to GK's contain user ID and a presenceinformation. FIG. 3 shows the relationship between the GK and the PAS.

[0033] As earlier mentioned, PP is the interface between the H.323 GKand the PAS. This protocol could be part of a standard service API likeParlay, an extension to H.323, XML based or based on other applicableprotocols. The exact syntax and transport mechanism for this protocol isoutside the scope of this invention.

[0034] The PP interface consist of the following components:

[0035] RegistrationInfo. Info sent by the client (GK). This infocontains a user ID, GK ID with an operation: register or unregister.

[0036] RegistrationInfoAck. A response to RegistrationInfo containingpresence information for the registered user.

[0037] PresenceNotification. The event could be triggered by PAS when aRegistrationInfo message is received. This event contains a user ID andpresence information.

[0038] According to a preferred embodiment, the present invention isrealized by using H.323 Annex K. Annex K describes a service independentHTTP based transport channel where H.323 messages are used fortransporting the URL for the services.

[0039] Realisation of a presence service based on Annex K is shown onFIG. 4. Given that the user A has received an URL from its serviceprovider.

[0040] During the registration procedure, the terminal of user A sends aRRQ message to user A's GK, (1). Parts of the registration informationis encapsulated in a RegistrationInfo message and sent to the PAS, (2).The PAS returns an URL pointing to User A's compiled presence list tothe user's GK in RegistrationlnfoAck (3). The gatekeeper will theninclude this URL in the ServiceControlSession structure in the RCF (4).

[0041] At the same time the PAS will send notifications to all usersthat are subscribing to registration events for User A. This is done bysending a PresenceNotification to the gatekeepers of these users inwhich a URL pointing to an updated presence list (5) for each of theseusers is included.

[0042] The gatekeepers will in turn send a ServiceControlIndicationmessage to the users endpoints (6), which will display/refresh the URLto get the latest presence information.

[0043] Unregistration is handled in a similar way. The RegistrationInfomessages will have status unreg instead of reg, and no URL will bereturned in RegistrationInfoAck. (5) and (6) will be the same.

[0044] The present invention in the H.323 system is a supplement toalready existing registration functionality. The registrationfunctionality is extended with additional services allowing the user tobe provided with information about the current registration of his/hersfriends and to “publish” information about own registration.

[0045] The present invention make use of the registration statusinformation already stored in the Gatekeepers. Then the users may bevisible for other users in a presence application just as they areattached to a Gatekeeper.

[0046] The invention is also applicable in conjunction with locationfunctionality. The additional information about users physical locationin terms of e.g. GPS (Global Positioning System) co-ordinates could betransferred to the PAS, assuming that the user terminal supports GPS.

[0047] In fact, there are no restrictions in what kind of informationthat might be attached to each user in the presence list.

[0048] Finally, according to the present invention, it should bepossible to let the same PAS also handle presence information fromothers than H.323 users, e.g. SIP users.

REFERENCES

[0049] ITU-T Recommendation H.323, Packet-Based MultimediaCommunications Systems, version 4.

[0050] ICQ (http://web.icq.com/)

[0051] M. Handley/H. Schulzrinne/E. Schooler/J. Rosenberg, “SIP: SessionInitiation Protocol”, RFC 2543, IETF; March 1999.

[0052] J. Rosenberg et. al., “SIP Extensions for Presence”,<draft-rosenberg-impp-presence-00.txt>, IETF; June 2000. Work inprogress

[0053] A. Roach, “Event Notification in SIP”,<draft-roach-sip-subscribe-notify-03.txt>, IETF; February 2001. Work inprogress.

[0054] H.323 Annex K (HTTP based service Control Transport Channel)

1. Method for tracking a registration status of one or more users in acommunication network according to an H.323 standard, said usersassociated to a Gatekeeper (GK) administrating registrations andunregistrations of said users, each user accessing the communicationnetwork through an associated EndPoint of the communication network,characterized in sending a first message from said Gatekeeper to aPresence Application Server (PAS), holding a presence list for each ofthe users, each time one of the users changes registration status in thecommunication network, said first message includes a user identificationof the current user, a Gatekeeper identification, and the change ofregistration status for said user, returning, from said PAS to said GK,a URL pointing to the presence list of said user, updating those of saidpresence lists affected by the change of the registration status of saiduser accordingly, sending, from said PAS, a second message to theGatekeeper notifying the Gatekeeper about the updating.
 2. Methodaccording to claim 1, characterized in that a first user is included ina presence list corresponding to a second user if all of the followingthree criteria are fulfilled: the first user is registered, through saidone or more Gatekeeper, in the communication network; the first user isincluded in a request list corresponding to the second user; the seconduser is included in a trust list corresponding to the first user. 3.Method according to claim 1 or 2, characterized in that said requestlist corresponding to the second user is a predefined list including allusers for whom the second user wants to track the registration status.4. Method according to one of the preceding claims, characterized inthat said trust list corresponding to the first user is a predefinedlist including all users that the first user allows to be notified whenthe first user changes registration status.
 5. Method according to oneof the preceding claims, characterized in that communication between thePAS and the Gatekeeper is carried through by means of a PresenceProtocol (PP) wherein the PAS act as a server and is each GK as aclient.
 6. Method according to one of the preceding claims,characterized in the following step after the step of sending the secondmessage: sending a third message from the Gatekeeper to the users whosepresence lists have been updated, said third message adapted to refresha URL, localized in each of those user's EndPoints pointing to theassociated presence list.
 13. Method according to one of the precedingclaims, characterized in that the PAS is adapted also to handle presenceinformation concerning users connected to communication networks notsupporting the H.323 standard.